1. Field of the Invention
This invention relates to a sliding property improving agent which is especially applicable to thermoplastic resins and effectively improves the sliding property of the resins while not negatively affecting other physical properties, mechanical properties and thermal properties thereof. This invention also relates to a process for making the sliding property improving agents. Resins having improved sliding properties through the additional said improved resin of this invention may be widely used in the field of electrical and electro-mechanical industries, precision machine industries and automobile industries.
2. Prior Art
Resins are widely used in many industrial fields as an alternative for metal materials because of their mechanical and electrical characteristics, productivity, anti-corrosive properties, anti-abrasion properties and their lighter weight.
One of the advantages of using a resin is its sliding property and the resins having self-lubricating properties are in practical use in the fields of the automobile industry, building industry and electrical industry. Both thermoplastic resins and thermosetting resins are used where sliding properties are required, and thermoplastic resins are especially widely used because of the ease and economics of that fabrication.
Recently, a requirement of improved sliding properties has increased as the area of use of the resin expands.
Attempts have been made to improved the sliding properties of resins and it has been well known as a method of improving sliding properties of resins to add a solid or a liquid luburicant thereto.
The following are some examples of various kind of resins having improved sliding properties by the addition of lubricants or various resins.
Japanese laid open 87-253650 (Kokai Sho 62-253650) and 88-37198 (Kokai Sho 63-37198) disclose a composition for improving the sliding properties of a polyoxymethylene resin comprising a poly-acetal polyethylene with a specific MI (melt index) and a conductor which reduces the coefficient of friction and noise while sliding .
Japanese laid open 88-33465 (Kokai Sho 63-33465) discloses a polyoxymethylene resin composition procduced by uniformly dispersing a ultra high molecular weight fine polyethylene powder having high moldability properties, anti-friction properties and anti-abrasion properties.
Japanese laid open 85-144351 (Kokai Sho 60-144351), corresponding to U.S. Pat. No. 4,670,508, discloses a thermoplastic resin composition comprising a melt mix product of polyoxymethylene and ultra high molecular weight polyethylene powder with specified properties, which have excellent abrasion resistance, impact resistance and a high critical PV limit.
Japanese laid open 87-253651 (Kokai Sho 62-253651), corresponding to U.S. Pat. No. 4,663,391, discloses a polycarbonate resin composition comprising an aromatic carbonate resin and a partially fluorinated polyolefin composition which exhibits improved wear resistance. Japanese laid open 88-16756 (Kokai Sho 63-162756) discloses a polycarbonate resin composition comprising an aromatic carbonate resin and a fluorinated polyolefin, a polyolefin, or a silicone liquid composition which also exhibits improved wear resistance.
Japanese laid open 88-182361 (Kokai Sho 63-182361) discloses a styrene resin composition containing rubber-modified styrene resin, polyolefin resin, styrene-olefin graft or block copolymer and dimethylsilicon having improved sliding properties, and Japanese laid open 89-201351 (Kokai 01-201351) discloses a styrene resin composition having an improved sliding property which contains silicone oil and a tin stabilizer and is used for sliding parts of a gear or a cam.
With regard to improving the sliding properties of thermoplastic polyester resins. Japanese laid open 84-170138 (Kokai Sho 59-170138) discloses a polyester resin having improved sliding properties containing a thermoplastic polyester resin, solid lubricant, lubricating oil and polyoxyalkylene compounds. Japanese laid open 89-140253 (Kokai Sho 59-140253) discloses a polybutylene terephthalate resin composition used as a frictional material which is prepared by adding potassium titanate fiber and fluorocarbon resin to polybutylene terephthalate resin and has improved sliding property. Japanese laid open 88-213551 (Kokai Sho 63-213551) discloses a resin composition containing polybutylene terephthalate resin mixed with tetrafluoroethylene resin, reinforcing material and solid lubricant. Japanese laid open 88-297455 (Kokai Sho 63-297455) discloses a polyester resin composition containing dispersed carbon fiber and ultra high molecular weight polyethylene having good sliding properties.
For improving the sliding properties of polyarylene sulfide resins, Japanese laid open 75-119040 (Kokai Sho 50-119040) discloses a polyphenylene sulfide resin containing tetrafluoroethylene resin as a lubricant.
Japanese laid open 77-129761 (Kokai Sho 52-129761) and Japanese patent publication 81-50124 Kokoku sho 56-50124) disclose a polyphenylene sulfide resin containing graphite a polytetrafluoroethylene resin and lubricating oil as a lubricant.
Japanese laid open 76-28145 (Kokai Sho 51-28145) and Japanese patent publication 82-13586 (Kokoku sho 57-13586) disclose a polyphenylene sulfide resin containing a molybdenum disulfide and a carbon fiber having improved sliding properties.
Japanese laid open 85-228558 (Kokai Sho 60-228558) discloses a polyphenylene sulfide resin containing a fiber reinforcement agent, tetrafluoroethylene resin powder, and an inorganic filler having cleavage properties.
Japanese laid open 87-232457 (Kokai Sho 62-232457) discloses a polyphenylene sulfide resin containing a tetrafluoroethylene resin, a reinforcing filler and a specified organic silane.
For improving sliding property of polyamide resins, Japanese laid open 85-96649 (Kokai Sho 60-96649) corresponding to U.S. Pat. No. 4,563,495, discloses a polyamide resin containing a high density polyethylene powder, and potassium titanate whiskers having good sliding properties. Japanese laid open 85-144351 (Kokai Sho 60-144351), corresponding to U.S. Pat. No. 4,670,508, discloses a polyamide resin mixed with a ultra high molecular weight polyethylene powder having a specified particle size having good sliding properties. Japanese laid open 87-218453 (Kokai Sho 62-218453) discloses a polyamide resin mixed with a carbon fiber and a specified molecular weight polyethylene.
Further a for improving sliding properties of polyphenylene ether resins, Japanese laid open 85-186560 (Kokai Sho 60-186560) discloses a polyphenylene ether resin blended with a polyamide elastomer having improved frictional and abrasion properties.
For improving the sliding properties of polyarylate resins, Japanese laid open 84-179662 (Kokai Sho 59-179662) discloses a polyarylate resin containing a lubricating oil, a lubricating oil carrier, mica, and a solid lubricant.
However, there are defects in the above mentioned prior art. For instance, in the compositions for improving the sliding properties of a polyoxymethylene resin disclosed in Japanese laid open 87-253650 (Kokai Sho 62-253650) and Japanese laid open 88-37198 (Kokai Sho 63-37198), the polyethylene is melted, then kneaded and dispersed into a polyoxymethylene resin but the compatibility of polyethylene with polyoxymethylene is not large enough so that the basic nature and properties of the resin, such as mechanical strength and heat resistance are adversely affected. Moreover, a surface of the molded product often causes delamination and the mixed resin adheres to the cavity of the mold after molding.
A thermoplastic resin composition comprising a mixed melt product of polyoxymethylene and ultra high molecular weight polyethylene powder with specified properties is disclosed in Japanese laid open 85-144351 (Kokai Sho 60-144351), corresponding to U.S. Pat. No. 4,670,508, in which ultra high molecular weight polyethylene powder is dispersed in the system as comparatively large sized particles. The reduction effect of the friction coefficient of the resin is not successful.
Polycarbarbonate resins disclosed in Japanese laid open 87-253651 (Kokai Sho 62-253651) and Japanese laid open 88-162756 (Kokai Sho 63-162756) have improved sliding properties by blending in a fluorinated polyolefin solely, or by blending in a fluorinated polyolefin, a polyolefin and a silicone liquid composition, and exhibit improved wear resistance. However, compatibility of the polycarbonate resin with the fluorinated polyolefin, a polyolefin, and a silicone liquid is not large enough. Consequently, preferable physical and mechanical properties of the polycarbonate resin are adversely affected and the resulting products show a bleeding phenomenon, surface delamination or adhering to a cavity of the mold.
Although a styrene resin composition containing rubber modified styrene resin, polyolefin resin, styrene-olefin, graft or block copolymer and dimethylsilicon disclosed in Japanese laid open 88-182361 (Kokai Sho 63-182361), exhibits a slightly improved sliding property, the resultant product resin does not exhibit good mechanical properties and shows surface delamination and bleeding phenomena, which are all adverse effects.
A styrene resin composition blended with silicone oil and tin stabilizer, disclosed in Japanese laid open 89-201351 (Kokai Hei 01-201351) exhibits an improved anti-burning property during molding but the effect of decreasing of the burned phenomenon of resin when molding is still not satisfied.
A thermoplastic polyester resin containing solid lubricant, lubricating oil and polyoxyalkylene compounds and disclosed in Japanese laid open 84-170138 (Kokai Sho 59-170138), exhibits a slightly improved sliding or friction resistance property but lubricating oil often forms at the surface of the products and the surface thereof becomes sticky.
Thermoplastic polyester resins blended with a fluorine resin or a ultra high molecular weight polyethylene having improved sliding properties disclosed in Japanese laid open 84-140253, 88-213551 and 88-297455 exhibits a slightly improved sliding property but compatibility of the fluorine resin or ultra high molecular weight polyethylene with the thermoplastic polyester resins is not large enough so the basic nature and properties of the thermoplastic polyester resin are adversely affected. Specifically, the mechanical strength thereof is badly affected, surface delamination of the products occurs and the mixed resin adheres to the cavity of mold after molding.
A polybutylene terephthalate resin composition prepared by adding potassium titanate fiber and fluorocarbon resin thereto disclosed in Japanese laid open 89-140253 (Kokai Sho 59-140253), a resin composition containing polybutylene terephthalate resin mixed with tetrafluoroethylene resin, reinforcing material and solid lubricant disclosed in Japanese laid open 88-213551 (Kokai Sho 63-213551) and a polyester resin composition containing dispersed carbon fiber and ultra high molecular weight polyethylene disclosed in Japanese laid open 88-297455 (Kokai Sho 63-297455) all exhibit improved sliding properties but because of poor compatibility of the tetraluforoethylene resin and of the ultra high molecular weight polyethylene with the thermoplastic polyester resins, the thermoplastic polyester resins could not exhibit basic physical and mechanical properties and, more than that surface delamination and adhesion to the cavity of the mold were big problems.
Polyarylene sulfide resins disclosed in Japanese laid open 75-119040, 77-129761, Japanese patent publication 81-50124, 82-13586, and Japanese laid open 85-228558, containing tetrafluoroethylene resin or a solid lubricant such as molybdenum disulfide and graphite exhibit a slightly improved sliding property but abrasion resistance of these resins decreases when a comparatively large amount of the solid lubricant is added. Especially, when tetrafluoroethylene is blended with a polyarylene sulfide resin, the compatibility of the tetrafluoroethylene with the polyarylene sulfide resin is not sufficient and the mechanical properties and surface conditions of the resultant resin decreases as the tetrafluoroethylene sometimes coagulates and does not become uniformly dispersed.
To solve the problem of poor compatibility of the tetrafluoroethylene with the polyarylene sulfide resin, a specified organic silane is added as disclosed in Japanese laid open 88-232457 but the result is still not satisfactory.
Polyamide resins disclosed in Japanese laid open 85-96649, 85-144351 and 87-218453 containing a high density polyethylene resin, an ultra high molecular weight polyethylene or a polyethylene for the purpose of improving the resins sliding properties, have defects in physical and mechanical properties the resin adheres to a cavity of a mold after molding and the delamination of the surface of the product sometimes occurs because the compatibility of the polyethylene resin with the polyamide is not essentially large enough.
Polyphenylene ether resins disclosed in Japanese laid open 85-186560, exhibit a slightly improved abrasion resistance but the coefficient of friction of the resin is not improved.
Polyarylate resins disclosed in Japanese laid open 84-179662 shows improved frictional and anti-abrasion properties but lubricating oil bleeds out to the surface thereof and causes damage to the surface and the mechanical properties of the resins decreases because of the poor compatibility of the lubricating oil and solid lubricant with the resins.
As discussed above, thermoplastic resins having improved sliding properties by adding conventional solid or liquid lubricants or various resins lost their basic mechanical properties.
The objective of the present invention is to provide a sliding property improving agent which does not adversely affect the mechanical strength of the resin.